Manufacture of paper



Patented June 2, 1931 UNITED STATES PATENT orr ca 'EABOLD R. CB-AITON, OF LAWRENCE, MASSACHUSETTS, ASSIGNOR TO BAIFOLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS mnrac'runn or Paras No Drawing. Application filed November 15, 1928, Serial No. 319,721. Renewed January 21, 1981.

The prlncipal object of my invention is to provide a method for incorporating into pa- 5 per filled with alkaline filler certain normally soluble constituents in a substantially insoluble form. ,1

An important object of my invention is the incorporation of sodium silicate in the form of an insoluble material into paper filled with alkaline filler. v

A further object of my invention is to provide a process wherein sodium silicate is reacted upon by a precipitant, such as alum, and

the resultant alum-sodium silicate reaction roduct is added to a paper mix containing fibrous material and alkaline filler at the wet end of the paper machine.

Other objects and advantages of the invention will become apparent during the course of the following description. y

In my copending applications 319,719 and 319,720, both filed November 15, 1928, I have shown that where a soluble material such as sodium silicate is incorporated into a fibrous mix, and there is added to such mix an agent, i such as alum, which serves to react with the soluble material to form a substantially insoluble compound, the substantially insoluble compound so formed is deteriorated-even to the point of destruction if alkaline filler is present in the paper mix. I have also made reference in such ap lications to the reason why incorporation of such material is desirable in paper making practice. Moreover 'in my copending applications referred to have described and claimed two methods by which this deterioration due to the alkaline filler can beovercome or avoided. In the present application I disclose a third method whereby a precipitate, such as an alum-sodium silicate-precipitate may be incorporated into pjaper containing a aline filler,- and where y the advantageous effect of such a precipitate may be imparted substantially undeteriorated to the paper stock and the paper made therefrom. The alum-sodium silicate precipitate or reaction product may herein be referred to as aluminum silicate without thereby being limited to any definite formula for this compound.

I have discovered that it is possible to avoid the deterioration or destruction of the efl'ect of such a recipitate by alkaline filler by mixing a solu 1e material such as sodium silicate and a precipitant therefor, such as alum, both preferably in dilute solution, in a separate container and adding the resulting product, preferably continuousl at the wet end of the paper machine to the brous mix containing alkaline filler. I

i In the preferred practice of my process I mixfin a separate container a solution of so,- dium silicate, preferably with an excess of a solution of alum, i. e., an amount above that which will eiiect a maximum precipitation The precipitate may be separated as by filtrationfrom the'precipitatin bath and used in this condition, or it may e dried and .em-' ployed in the dried condition after suitable comminution, but these procedures'are unnecessary as the soluble by-products of the alum-sodium silicate reaction do not appear to be detrimental to my process. The precipitate, therefore, together with the accompanying liquid in a separate container is added preferably continuously at the wet end of the paper machine to a fibrous mix containing alkaline filler. There may be present in the fibrous mix, in addition to the fibrous material and alkaline filler, other material which may be present in the papermaking process such as coloring matter or sizing, for example rosin size either as such or originally precipitated, as by alum.

In view of the fact that it is sometimes difiicult to disperse flocks of the alum-sodium silicate preci itate, and to-dlstribute them. properly in t e fibrous mil to impart substantially uniformly the effect of the said precipitate to the stock and the paper made therefrom, I prefer to pass the precipitate prior to its addition to' the fibrous mix through a dispersing or disintegrating machine such as a colloid mill.

In one modification of my process I have found it advantageous to effect the mixing of sodium silicate andalum in the presence of other material which may be insoluble, such as fibre or clay, or in the presence'of material which may be soluble, preferably colloidally soluble, such as starch or glue. In such modification, the entire resulting product is added as in the previous instance at the wet end (if the paper machine to the fibrous stock containing alkaline filler. Where sodium silicate and alum are mixed in this manner. the precipitate resulting therefrom is produced either in a form which renders it readily dispersibleas when fibre or clay is used,

or in a form which is more finely dispersed as when starch or glue is used. In either event the result is that the precipitate is thus much more easily incorporated when added to the fibrous mix at the wet end of the paper machine.

By adding the alum-sodiumsilicate precipitate to'the fibrous mix containing alkaline fillerat the wet end of the paper machine, the precipitate is thus added at a point where there will be a minimum of intimacy and time of contact of the constituents of the mix before the web is formed. This is necessary as I have found that if the precipitate be added when the fibrous mix is in a relatively concentrated condition, and particularly when the relatively concentrated mix is subjected to agitation as is: normal in stock chests, the effect of the precipitate isvery quickly deteriorated, even to thepoint of com-, plete destruction. The efl'ect of the precipitate even when the mix is in diluted condition is gradually deteriorated but is substantially unaffected withinthe time limits that the mix is maintained in the dilute state in the usual papermaking procedure. .Moreover although agitation in the dilute state hastens to a certain extent the deterioration of this effect, the speed of deterioration is not nearly so pronounced as in the concentrated condition, and from a practical stand An illustrative furnish suitable for use in the practice of my process is as follows:

Materials added in the beater 1 Pounds Fibrous furnish (air dry basis), e. g. sulphite and soda p lp 1700 Alkaline filler (bone dry basis), e. g. calcium carbon- 300 Another illustrative furnish is as follows:

Materials added in the beater Pounds arts of sulphite pulp. soda pulp and 01d paper stoc 1460 Alkaline filler (bone dry basis), e. g. calcium carbon- 800 ate magnesium hydroxide Materials mired in separate container, and the midture added proportionately and continuously to the fibrous min on dilution Pounds Fibre (air dry basis) e. g. equal parts of sulpblte pulp soda pulp and old paper stock 240 Inorganic alkali metal salt, e. g.- 60 B. sodium sili- Fibrous furnish (air dry basis), e. g. equal ca Precipitant, e. g, a'lnm However, I do not by any means restrict my invention to the above formulae which are intended as illustrative only and not limiting, I

nor to any definite quantities of sodium silicate or ratio of sodium silicate to alum, as I have found my invention may be satisfactorily employed with widely varying amounts of sodium silicate with a wide variation of the ratio of sodium silicate to alum, but of course, from the standpoint of economy I prefer to use the least amounts of sodium silicate and alum which experience indicates under given conditions will produce the desired result.

The herein described method of incorporating the precipitate of alum-sodium silicate into paper filled with alkaline filler, may be used alone, or it may be used suitably in connection with other of my copending applications, e. g. Serial Nos. 304,171 and 304,174, filed September 5, 1928, and particularly with those having to do with producing sized paper filled with alkaline filler, e. g. applications Serial Nos. 304,168 and 304,172, filed September 5,1928.

. Of course instead of mixing the sodium silicate and alum in a separate container, streams of these materials may be so arranged as to impinge on one another and the resultant stream be directed into the paper mix at the wet end of the paper machine. This procedure oifers no special advantage; as a matter of fact, the mixing of the sodium silicate and alum is apt to be less complete under this condition than when a separate container is used. Therefore I consider this variation the substantial equivalent of mixing of the sodium silicate and alum in a separate container. 7 p,

I have found that sodium silicateis merely a representative of a class of substances which presses their hydroxyl ion concentration.

Sodium silicate has already been cited as one example of such a class of substances. An-

other example is sodium stannate.

As a precipitantfor the sodium silicate or equivalent substance, I may use any ma-.

terial which depresses the hydroxyl ion concentration thereof in the place of alum, for example, acidic material such as sulphuric acid, or sodium bisulphate (NaHSO,), or a salt of a trivalent metal such as ferric iron, or the other salts of aluminum. I may also employ ammonium salts such as ammonium chloride or sulphate. However, from the sta-ndpoints of cost and efliciency I prefer to use the ordinary aluminum sulphate commonly known as alum.

Where I use the expression alkali metal,

I mean to include the hypothetical alkali 25 7 metal ammonium (NH By the term alkaline filler I mean sub stantially water insoluble filler which when agitated in contact with freshly boileddistilled water, say for an hour, will impart a pH value to such water greater than 7 .0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416, issued August 12, 1926; calcium'carbonate magnesium hydroxide disclosed in my United States Patent No. 1,415,391, issued May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals, (which expression is herein intended to include magnesium) or compounds, double salts, or physically associated mixtures of these with one,

or more other acid soluble materials of a substantially water insoluble nature. 7

By the'term alkaline filler I also intend toinclude fibrous material and/or other material such as paper coating constituents or the like containing one or more compounds of the character referred to, such as old papers or similar papers, broke, or the like. When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or

other forming, felting, shaping or molding machine.

By the term wet end of the paper machine I intend to include those instrumentalities employed in paper manufacture by which and/or in which a relatively concentrated paper mix is diluted, and treated, conveyed or fed up to the point of web formation, such as the mixing box, regulating and proportioning devices, rifllers, troughs, screens, head boxes, inlets, and the llke, 1ncluding also instrumentalities used in the white water cycle.

While I have described in detail the preferred embodiment of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and'the arrangement of steps may be widely varied without departing from the spirit of my invention or the scope of the subjoined claims.

I claim: 1

1. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl ion concentration, and a precipitant therefor,

comprising separately -mixing said alkali.

metal salt and said precipitant, adding the resulting product to fibrous material and a.l-

kaline filler under conditions favoring the minimizing of time of contact of the constit-1 uents of the mix, and thereafter making paper therefrom.

2. The method of incorporating into pa; per filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitablev by material which depresses its hydroxyl ion concentration, and a precipitant therefor, comprising separately mixing said alkali metal salt and said precipitant, adding the resulting product tofibrous material and alkaline filler underconditions favoring the minimizing of intimacy and time of contact of the constituents of the mix, and thereafter making paper therefrom. 1

3. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl ion concentration, and a precipitant therefor, comprising separately mixing said alkali metal salt and said precipitant, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom. y 7 4. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl ion .concentration, and a precipitant therefor,

taining alkaline filler, and thereafter making paper therefrom.

5. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material which depresses its hydroxyl ion concentration, and acidic material, comprising separately mixing said alkali metal salt and said acidic material, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

6. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, and a salt of a trivalent metal comprising separately mixing said alkali metal salt and said salt of a trivalent metal, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

7. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7 .0, which is precipitable by material whichdepresses its hydroxyl ion concentration, and a salt of aluminum, com

prising separately mixing said alkali metal salt and said salt of aluminum, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

8. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a H value greater than 7 .0, which is precipita 1e by material which depresses its hydroxyl ion concentration, and alum, comprising separately mixing said alkali metal salt and said alum, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

9. The method of incorporating into paper filled with alkaline filler the recipitate of sodium silicate and a precipltant therefor comprising separately mixing sodium sili cate and said precipitant, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom. V I

10. The method of incorporating into paper filled with alkaline filler the precipitate of sodium silicate and alum comprising separately mixing sodium silicate and alum, add ing the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

11. That step in a method of incorporating precipitated aluminum silicate into paper filled with alkaline filler comprising adding precipitated aluminum silicate at the wet end of the paper machine.

12. That step in a method of incorporating precipitated aluminum silicate into paper filled with alkaline filler comprising adding precipitated aluminum silicate and alum at the wet end of the paper machine.

13. The method of incorporating into paper filled with alkaline. filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, and a precipitant therefor, comprising separately mixing said therefor,'comprising separately mixing said alkali metal salt and said precipitant in the presence of other material, adding the resulting product at the wet end of the paper ma-' chine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

15. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its hydroxyl ion concentration, and a precipitant therefor, comprising separately mixing said alkali metal salt and said preci itant 1n the presence of colloidal material, a ding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom. i

16. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7.0, which is prepresence of colloidally soluble material, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

17. The method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a. pH value greater than 7 .0, which is precipitable precipitant in the presence of other material,

adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter making paper therefrom.

19. The method of incorporating into paper filled with alkaline filler the precipitate of sodium silicate and alum comprising mixing sodium silicate and alum in the presence of other material, adding the resulting product at the wet end of the paper machine to a fibrous mix containing alkaline filler, and thereafter makin paper therefrom.

20. The method of incorporating into paper filled with alkaline filler the precipitate of sodium silicate and a precipitant therefor comprising mixing sodium silicate and said precipitant, adding the resulting product at the wet end of the paper machine to a fibrous mix comprising soda and sulphite pulp and containing alkaline filler, and thereafter making paper therefrom. v

21. The method of incorporating into paper filled with alkaline filler the precipitate of sodium silicate and a precipitant therefor comprising mixing sodium silicate and said precipitant, adding the resulting product at the wet end of the paper machine to a fibrous mix comprising soda and sulphite pulp and old paper stock and containing alkaline filler, and thereafter making paper therefrom.

22. That step in the method of incorporating into paper filled with alkaline filler the precipitate of an inorganic alkali metal salt with a pH value greater than 7.0, which is precipitable by material which depresses its ydroxyl ion concentration, and a precip1- tant therefor comprising adding the product resulti from mixing said alkali metal salt and sai precipitant at the wet end of the paper machine.

23. That step in a method of incorporating into sized paper filled with alkaline filler a precipitate produced from sodium silicate comprising adding at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler and sizing material, the previously produced reaction product of sodium silicate and a precipitant therefor.

24. That step in a. method of incorporating into sized paper filled with alkaline filler a precipitate oduced from sodium silicate comprising ding at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler, and rosin size, the previously produced reaction product of sodium silicate and a precipitant therefor.

25. That step in a method of incorporating into sized paper filled with alkaline filler a precipitate produced from sodium silicate comprising adding at the wet end of the paper machine to a paper mix including fibrous material, alkaline filler and rosin size previously precipitated by alum, the prevlously produced reaction product of sodium silicate and a precipitant therefor.

In testimonv whereof I aflix my signature.

HAROLD ROBERT RAFTON. 

